The invention relates to an apparatus for making monochromatic or polychromatic decorations on traditional-type waterproof tarred membranes, used for surface covering in the building industry.
Obviously the invention is only intended for use in connection with surfaces that will be on view, so it finds particular application on roof or terrace covering and the like.
Normally membranes used for such purposes, known as "self-protecting", are surface-treated with mineral grits, or plastic or metal scales, sands or granules, all of which protect the membranes from weathering caused above all by the sun's ultraviolet rays.
The invention is intended for application to membranes of the above-mentioned type which remain on view, and makes use of the above materials.
Hoppers are normally used to apply the layer of grit on the tarred membrane, usually in conjunction with a cylindrical roller having a smooth or slightly corrugated surface, which is positioned below the outlet mouth of the hopper and on the tarred membrane moving below it. The grit falls by force of gravity on to the roller and is conveyed by the latter on to the membrane, being distributed thereupon uniformly so as to form a protective layer. Using this method no decorative pattern on the membrane is possible.
The known system for making decorations on the surface of the membrane with grit envisages the use of one or more hoppers which are mobile transversally with respect to the advancement direction of the membrane. The hopper movement thus consists in a side-to-side movement while the grit is being laid by the hopper itself on to the underlying membrane. This is a system that exhibits a considerable drawback, however, since the only decorations possible are those deriving from a combination of the two straight movements of the membrane and at least one hopper, mutually perpendicular, so that the decorations produced are extremely rudimentary, consisting essentially in straight lines, zig-zags and serpentine patterns.
The principal aim of the present invention is to obviate the above drawbacks in the prior art by providing an apparatus which simply and economically makes it possible to create any kind of design on tarred membranes using solid particles.